/*
 * Copyright (C) 2008 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect.testing.testers;

import static com.google.common.collect.testing.features.CollectionFeature.ALLOWS_NULL_VALUES;

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.collect.testing.Helpers;
import com.google.common.collect.testing.features.CollectionFeature;
import com.google.common.collect.testing.features.CollectionSize;

import java.lang.reflect.Method;
import java.util.Collection;

import org.junit.Ignore;

/**
 * Tests {@link java.util.Set#hashCode}.
 *
 * @author George van den Driessche
 */
@GwtCompatible(emulated = true)
@Ignore // Affects only Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.
public class SetHashCodeTester<E> extends AbstractSetTester<E>
{
    public void testHashCode()
    {
        int expectedHashCode = 0;
        for (E element : getSampleElements())
        {
            expectedHashCode += ((element == null) ? 0 : element.hashCode());
        }
        assertEquals(
                "A Set's hashCode() should be the sum of those of its elements.",
                expectedHashCode,
                getSet().hashCode());
    }

    @CollectionSize.Require(absent = CollectionSize.ZERO)
    @CollectionFeature.Require(ALLOWS_NULL_VALUES)
    public void testHashCode_containingNull()
    {
        Collection<E> elements = getSampleElements(getNumElements() - 1);
        int expectedHashCode = 0;
        for (E element : elements)
        {
            expectedHashCode += ((element == null) ? 0 : element.hashCode());
        }

        elements.add(null);
        collection = getSubjectGenerator().create(elements.toArray());
        assertEquals(
                "A Set's hashCode() should be the sum of those of its elements (with "
                        + "a null element counting as having a hash of zero).",
                expectedHashCode,
                getSet().hashCode());
    }

    /**
     * Returns the {@link Method} instances for the test methods in this class which call {@code
     * hashCode()} on the set values so that set tests on unhashable objects can suppress it with
     * {@code FeatureSpecificTestSuiteBuilder.suppressing()}.
     */
    @GwtIncompatible // reflection
    public static Method[] getHashCodeMethods()
    {
        return new Method[]{
                Helpers.getMethod(SetHashCodeTester.class, "testHashCode"),
                Helpers.getMethod(SetHashCodeTester.class, "testHashCode_containingNull")
        };
    }
}
